Studies of the roles of progesterone and prolactin in the regulation of broodiness and cyclic reproductive activity of turkeys are proposed. Purification of turkey prolactin, the development of a radioimmunoassay for turkey prolactin and for progesterone will be carried out. These assays will be used to study the normal cyclic changes in circulating prolactin and progesterone during the ovulatory cycle of the turkey, during the period just preceding sexual maturity, during the incubation period and particularly at the time just prior to the onset of incubation. The effects of hormonal and environmental treatments, capable of interrupting broodiness, on circulating levels of progesterone and prolactin will be determined.